Field of the Invention
The invention relates to a method of driving a machine related to printing technology.
German Published, Non-prosecuted Patent Application DE 42 10 988 A1 describes a multi-motor drive for a printing press wherein a rotary encoder is assigned to each motor. The rotary encoders generate signals relating to the rotary position of a respective element to which a torque is fed in a gear mechanism or transmission of the printing press. The rotary encoder signals are fed to phase measuring devices, by which the phase difference between adjacent feed points are determined. Depending upon the phase difference, the motors are driven in such manner that elastic stresses in the gear train can be kept constant. Controlling the stress between two adjacent feed points ensures continuous tooth surface or flank contact in the gear train and therefore has a positive effect upon maintenance of register, but only a slight effect upon vibration characteristics of the printing press.
In a method disclosed in German Published, Non-prosecuted Patent Application DE 199 14 627 A1, corresponding to U.S. Pat. No. 6,401,620, for compensating for rotational oscillations of a printing press, opposing torques are infed at locations where rotational oscillations occur most intensely. The infeeding of opposing moments may be effected by driving a main drive motor or a separate motor, by which a variable-speed opposing torque component may be produced. The opposing torques to be infed are stored permanently in a control system and are changed only when the machine configuration is changed, so that the locations with the oscillations which occur most intensely occur with an offset.
It is accordingly an object of the invention to provide a method of driving a machine related to printing technology, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and which permits a suppression of undesired oscillations over a wide rotational speed range.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of driving a machine related to printing technology, which comprises providing movable elements forming a kinematic chain being coupled with one another via at least one gear mechanism. Torque components are fed in by a respective motor of at least one group of two motors respectively located at least at two elements associated with one another. The torque components have equal amplitude but opposite directions of rotation, for suppressing disruptive oscillations at least at the one group of two motors. The amplitude of the torque components is proportional to relative rotation of the two elements associated with one another. Rotary encoders are provided to obtain signals for reproducing rotational positions of the elements.
In accordance with another mode, the method of the invention further includes placing the motors, in at least the one group thereof, at the start and the end of the kinematic chain.
In accordance with a further mode, the method of the invention further includes driving the one group of two motors independently of signal processing of further motors.
In accordance with an added mode, the method of the invention further includes driving the motors of the one group, for shifting the natural frequency of the kinematic chain into a non-disruptive range.
In accordance with an additional mode, the method of the invention further includes providing a printing press having a large number of printing units forming the kinematic chain. A main drive torque is fed in by a main drive motor and a natural frequency is shifted by auxiliary drive motors forming a group.
In accordance with yet another mode, the method of the invention further includes providing the auxiliary drive motors for acting at the start and the end of the kinematic chain.
In accordance with a concomitant mode, the method of the invention further includes driving the auxiliary drive motors independently of the control of the main drive motor.
Applying and controlling additional motors, in particular electric motors, and using previously provided motors at one or more elements, also in addition to a main drive motor, makes it is possible to operate motors pairwise so that a torque output by one motor corresponds to that from a mechanical spring which is connected between two pairwise coupled motors. In the case of a printing press of in-line construction, having a multiplicity of printing units, an increase in the critical natural frequency of the printing press of 50% can be achieved, for example with two auxiliary motors at the start and the end of the printing press, and coupling these two drives via a previously provided gear train. Accordingly, the number of prints at resonance can be increased, for example, from the usual 10,000 prints per hour to 15,000 prints per hour. The pairwise coupled motors form an electromechanical spring which changes the natural form of the machine that is related to printing technology. The natural form can be influenced by a suitable selection of the stiffness or rigidity of such an electromechanical spring, so that the relative excursions and, therewith, the dynamic sectional torques in a gear train that couples the driven elements can be improved in the range that is critical for backlash. It is possible to realize or implement electromechanical springs, by which the natural frequency of a printing machine can be increased even further, by using a main drive motor in conjunction with auxiliary drive motors.
The method encompasses the possibility, depending upon the then occurring machine speed or upon other parameters, such as the machine configuration, of the connection or disconnection of the electromechanical springs or the use of various combinations. A linear damping characteristic between pairwise connected machine elements can also be realized or implemented by the motor control system, in addition to the spring characteristic, in order to increase the oscillation damping. For this reason, the method can advantageously be combined with electrical infeeding of compensation torques.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of driving a machine related to printing technology, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.